EP1275502A1 - Control patches for multi-colour gravure printing - Google Patents

Abstract

Control strip or block with an arrangement of control fields for checking and control of multi-ink printing with a gravure printer. The control strip comprises control fields (6) with first (5) and second (4) partial control fields, whereby the first partial field comprises color gray value balance fields from cyan, magenta and yellow, while the second partial fields are uncolored black raster fields with tone values from 0 to 100 percent. The tone values of the first and second control fields are chosen so that individual combined control fields appear as a single color surface.

Description

The present invention relates to a control strip or control block containing an arrangement of control fields to control and / or control the multi-color printing of a Intaglio printing process.

In gravure printing, the color concentration (relative composition of the printing inks is off Color concentrate, blend and solvent) one of the most important parameters that controls Need to become. It has a decisive influence on the coloring of the process as well as the color and tonal quality of the printed product. The color concentration again depends on the nature of the substrate to be printed on which one a certain color impression is to be created. Quality is becoming practical today assessed exclusively by eye and with the aid of densitometers.

The quality check is carried out using control strips or control blocks, which consist of an arrangement of control fields.

The arrangement of several control fields becomes control strips or control blocks called. According to DIN 16527 Part 1, March 1993, a one-dimensional one is placed under a control strip Line up of control fields understood. A control block is analogous to this a two-dimensional arrangement of control fields. There are single color prints or Control strips intended for single-color printing as well as multi-color printed or for control blocks intended for multicolor printing. Control strips, the only are intended for the control, regulation or regulation of printing, are specifically called Print control strips, those that are used exclusively for monitoring the copy, are called specifically copy control strips, while strips that can serve both purposes are only referred to as control strips.

According to DIN 16527 Part 1, a control field is an area on which to test purposes one or more picture elements are arranged, the latter can e.g. Halftone dots, Be lines or full tones, the term control field refers to DIN 16 527 part 1 a test area that is directly visible on a flat substrate (e.g. a film) Form is transferred, regardless of whether the information is previously in analogue (e.g. film) or digital Form (e.g. magnetic memory, optical disc) saved.

Control strips and control blocks are used for visual or metrological control of copying and printing processes, e.g. for the proof or edition print on Printing machines according to the principles of planographic printing, gravure printing, letterpress printing or By pressure.

Another application of such control means is the control or regulation of the pressure during the production. The former application can be both visual and visual metrological evaluation of one or more control fields, the latter application only after metrological evaluation. This is done according to the state of the art Densitometers or color measuring devices, e.g. Spectrophotometer used. Both devices use a measurement spot to record those that are thrown back from a printed control field optical energy.

Control fields provided for measurement and / or visual evaluation exist either from a solid field, i.e. one fully printed or for full surface Printing area or a grid, i.e. one in printed or for printing intended grid points or lines of resolved area. Both full tones and screen tones can be single color or multi color. On the substrate to be printed A control field is called multicolored if it is printed by several overlapping Printing inks has arisen. Overprinting here means a pressure on which the same Surface inks of different colors are applied. As printing inks are here Pigment layers understood, for example as suspensions by a printing press be transferred to the substrate to be printed.

Printing inks whose pigments are the primary colors used for multi-color printing, e.g. Black (K), Cyan (C), Magenta (M), Yellow (Y) (yellow) in four-color printing, generate, designated one as scale printing inks.

A first category of control fields comprises the multi-colored control fields for visual assessment or measurement, e.g. the solid color fields of the secondary colors blue, Green, red, the tertiary color black, which is created by the overprint of the colorful Primary colors (CMY) are generated, as well as the gray balance fields.

The gray balance fields are according to DIN 16527 part 1. multi-colored grid fields, at which the color densities of the printing inks involved in such a numerical ratio stand that a manufactured under undisturbed, average printing conditions Pressure for the eye achromatic, i.e. appears neutral gray. Colorless-looking, printed Gray balance fields cannot be viewed from grid fields from a minimum viewing distance distinguish that are only printed with the achromatic ink black (K).

Another category of control fields are the single-color control fields of the Scale printing inks (CMYK) and, if necessary, special printing inks. These control fields enable the control of the optical density and the color location of the mentioned printing inks or special printing inks e.g. using a densitometer.

The geometry of the control fields is usually such that their shape matches that used Shape of the measuring spots of densitometers and other reflectometers is adapted. They are therefore rectangular in the case of measuring devices with an elliptical measuring spot and square, circular or hexagonal in the case of circular measuring spots.

The prior art discloses numerous sophisticated methods for checking printing results using the aforementioned control strips or control blocks. This However, processes mainly relate to offset printing processes and printing of paper, which are divided into classes according to specific guidelines.

In the field of packaging, however, there are a variety of packaging materials faced with different surfaces to be printed. Such surfaces can e.g. made of paper, plastic, metal or ceramic coatings.

However, the different substrate surfaces influence the color transfer from the Print form on the substrate in a decisive way.

In the gravure printing process, the printing areas are recessed compared to the non-printing areas in the printing form. The ink to be applied is in the printing depressions, the so-called grid cups. The grid cells are through so-called webs or web surfaces which are raised and accordingly do not bear any printing ink, mutually demarcated. In the case of halftone images, the grid cells are arranged in a grid a graded size. During the printing process, the color in the printing zone is removed from the Transfer the grid cells onto the substrate to be printed.

It is known that when printing raster images by gravure printing, the color elements from a certain tonal value, also called color coverage or color coverage value, tend to flow on the substrate to be printed and flood the substrate surface, which results in a higher tone value than that provided by the target value. The sudden increase in the tonal value caused by the flooding of the printing area is not to be confused with the so-called dot gain. The dot gain indicates how large the area coverage on the printed substrate compared to the Target value, for example based on a template, but based on the increase in size of the color elements on the printed substrate compared to the template and can all areas of coverage occur without sudden changes.

If you consider a raster graphic with a continuous increase in tonal values according to Target value, a so-called color jump occurs at a certain tonal value or tonal value range on, i.e. there is a sudden increase in the area coverage. The color jump is due to the aforementioned flooding of the grid area, i.e. the applied Color elements begin to flow into each other and combine with each other, wherein the spaces created by the webs or web surfaces are filled with printing ink become.

If, for example, the grid pattern consists of points, the point orders begin a certain area coverage to merge and between the Dots are formed by color bridges, which causes the color gaps to jump Increasing the area coverage with printing ink are completely covered. A consequently, a further increase in the tonal values above the flooding area only has an effect on the color density by increasing the layer thickness of the color.

The specified tonal values and converted to the printing form, in this text target values are therefore difficult to achieve in the area of such a color jump. It is therefore desirable to capture and locate this color jump to accordingly Being able to influence the printing process. Since the onset of the color jump very strongly on the nature of the substrate to be printed and the printing ink and depending on different process parameters, the problem of Only tackle color jumps individually for each printing process.

Control strips or control blocks of the prior art also have the disadvantage that that checking the optical density (color density) of each primary color only by measuring the single-color control fields (solid color field) of the primary colors using densitometers is possible. The color densities can therefore be measured using the aforementioned measurement method do not monitor continuously in the print run due to effort. However, it is desirable, the color densities of the primary colors should be continuous with as little effort as possible to monitor so that in the event of discrepancies for the purpose of fault detection, the monochrome Control fields of the primary colors (CMY) can be measured immediately.

The invention is therefore based on the object to be printed with regard to the most varied Materials or substrates, the arrangement of control fields of a control strip or control block for a gravure printing process and an arrangement of control fields to provide control of the density values of the Primary colors allowed, as well as a control field to record the color jump.

a) die ersten Kontrollteilfelder bunte Graubalancefelder aus dem Übereinanderdruck der Primärfarben Cyan (C), Magenta (M) und Yellow (Y) in abgestuften Tonwerten von 0-100% sind und

b) die zweiten Kontrollteilfelder unbunte Rasterfelder von Schwarz (K) in abgestuften Tonwerten von 0-100% sind,

und die Tonwerte des ersten und zweiten Kontrollteilfeldes eines Mehrbereich-Kontrollfeldes so gewählt sind, dass das Mehrbereich-Kontrollfeld als einheitliche Tonfläche erscheint und die beiden Kontrollteilfelder eines Mehrbereich-Kontrollfeldes unmittelbar und einander anstossend benachbart sind.According to the invention, the object is achieved in that the control strip or control block contains multi-area control fields, each with a first and second control subfield

a) the first control subfields are colored gray balance fields from the overprinting of the primary colors cyan (C), magenta (M) and yellow (Y) in graded tonal values from 0-100% and

b) the second control subfields are achromatic grids of black (K) in graded tonal values from 0-100%,

and the tonal values of the first and second control subfields of a multi-range control field are selected such that the multi-range control field appears as a uniform tone surface and the two control subfields of a multi-range control field are immediately adjacent to one another.

The color densities of the primary colors (CMY) are therefore monitored via gray balance control fields, whereby these are not measured densitometrically but visually by the Comparison with the neighboring achromatic black grid fields checked for constancy become. So you monitor the constancy of the gray balance fields and not how they are behavior of individual primary printing inks (CMY).

The first and second control subfield of a multi-range control field preferably have matching color values, i.e. a matching color impression.

The multi-area control fields essentially represent the structure of the gray axis of the primary colors CMY on the one hand and black (K) on the other.

The multi-area control fields are preferably in two parts. They are also preferably in the order of increasing or decreasing tone values, preferably immediately and arranged adjacent to one another, with the gray balance fields mutually lying adjacent on one axis and the achromatic black grid fields adjacent to each other are arranged lying on an axis.

The multi-area control panel is preferably rectangular or square. However, it can also be circular or elliptical, or a polygonal, e.g. hexagonal, structure exhibit.

The division of the multi-area control field into a first and second control subfield can be done in any way. The division should, however, be such that a direct visual comparison of the first control subfield with the second control subfield of the multi-range control field is possible.
the multi-area control field can, for example, be divided into a core area and an edge area as subfields, the core area preferably being dimensioned such that it can be measured with a color measuring device. For example, the gray balance fields and preferably the achromatic black grid fields can be arranged in the core area.

The multi-area control field is preferably in a rectangular or square shape and is divided into two rectangular control subfields of the same size as possible.

In a preferred embodiment of the invention, the control strip or control block also contains an arrangement of control fields in the form of single-color grids of the primary colors CMY with, preferably uniform, graded tonal values from 0-100%. That for each primary color becomes a control field for a certain number of tonal values in the range of 0-100% created.

The multi-range control fields and / or the single-color grids of the primary colors (CMY) preferably each contain a multi-range control field or control field as a full-tone field (100%).

The aforementioned single-color control fields of the primary colors (CMY) as well as the gray balance fields and thus also the achromatic black grids will be beneficial for the Tone values 5%, 20%, 40%, 60%, 80% and 100% created, where 100% corresponds to a solid field.

The control fields of the individual primary colors (CMY) are preferably in the order the increasing or decreasing area coverage, preferably immediately and arranged adjacent to each other.

The gray axis created from black (K) serves as a reference for the CMY gray axis (gray balance fields) with regard to color density at certain tonal values (taking into account the Dot gain). Result from the visual comparison of the two control subfields striking differences, that is, the gray balance fields contain a color cast, see above a discrepancy in the color densities of the primary colors (CMY) can be derived from this. This inconsistency can be caused, for example, by a disturbed color acceptance of one or several printing inks (CMY).

If such discrepancies occur, the full tone control fields can be used in a next step (100%) of the primary colors CMY measured the color densities using a densitometer and compared with the target values.

The arrangement of control fields according to the invention consequently permits continuous (visual) Monitoring the color densities of the primary colors CMY during the print run, without having to permanently measure the color densities of the primary colors CMY individually Need to become.

Due to the continuous checking of the gray balance fields, timely adjustment can be made the ink cylinder or the ink supply can be guaranteed.

Another aspect of the present invention relates to a control strip or control block, containing an arrangement of control fields for checking and / or controlling multicolor printing for a gravure printing process, the control strip or control block being a Contains a gradient control field in the form of a strip-shaped grid, and that Color gradient control field along its length the continuous course of the setpoints Reproduces tonal values from 0-100% and on the lateral longitudinal edge of the gradient control field the associated target values of the tonal values are listed in graded division.

The course of the nominal values of the degree of coverage of 0-100% is preferably linear.

Since the critical tonal value at which said color jump occurs, for a class of too printing substrates can each be in a similar tonal range, for such a class of substrates is also only a certain section of the tonal range from 0-100% can be printed as a control field.

For example, does the color jump always occur in a certain class of substrates Range from 70 to 90%, it is sufficient to use the checkbox for the substrate classes mentioned print only in the tonal range from 70 to 90%.

The color gradient control field allows the color jump in the visual or with a measuring device To continuously determine or control the grid and use the ones listed on the side Assign a tone value scale to a certain tone value or tonal value range (target value). Knowing this critical tone value or tone value range, for example in the specified tonal range in the print template in advance Be avoided.

The substrate to be printed is preferably a film, in particular a flexible packaging film. The packaging film can be transparent, translucent, opaque and / or colored or colored through. The packaging films can be colored, reflective or metallized Surface layers contain and optically colored, reflective and / or metallizing have acting surfaces.

The printable packaging films can be mono films or film composites. The packaging films layers or foils made of plastic, such as polyolefins, polyester, Polypropylenes, polyamides or from metals, such as aluminum, iron, steel or alloys of these, or of cellulose, such as paper, glassine, or cellulose, contain or consist thereof.

The surfaces to be printed can e.g. from one of the aforementioned papers, plastics or metals. Furthermore, the surface to be printed can have a ceramic coating his.

The thickness of the packaging material can e.g. from 5 to 1000 µm, especially from 7 to Amount to 200 µm.

The color densities of the individual primary colors (CMY) of the gray balance fields are preferred adapted the optical and / or mechanical properties of the substrate to be printed. The color densities of the primary colors (CMY) must therefore be used to create the Gray balance fields can be determined beforehand.

In a first step, a test form, e.g. an IT 8.7 / 3 test form according to ISO 300, created. The proof is made on the same substrate class as the following one Print run. The test form is then measured using a spectrophotometer. On the basis of the measured test form, a so-called ICC input profile (International Color Consortium). This means that the measured device values are in the device-independent L * a * b color space converted.

Based on the measured test form, the L * a * b values of the achromatic are subsequently black gray values determined. Then the. Based on the ICC input profile Gray values from CMY are calculated for the corresponding achromatic black gray values. The The values obtained are used as the basis for the subsequent print run.

Fig. 1:

Kontrollfelder der Primärfarben (CMYK) mit integrierten Graubalancefelder;

Fig. 2:

Farbverlauf-Kontrollfeld mit kontinuierlichem Verlauf des Tonwertes von 0-100%;

Fig. 3:

Mehrbereich-Kontrollfelder mit Kontrollteilfelder der Primärfarbe unbunt Schwarz (K) und der Graubalance.

The invention is explained in more detail below by way of example and with reference to the accompanying drawings. Show it:

Fig. 1:

Control fields of the primary colors (CMYK) with integrated gray balance fields;

Fig. 2:

Color gradient control field with a continuous gradient of the tonal value from 0-100%;

Fig. 3:

Multi-area control fields with control subfields of primary color achromatic black (K) and gray balance.

1 shows a particularly advantageous arrangement of control fields of a control strip according to the invention. The control fields with the reference symbols 1 to 4 represent single-color ones Grids of the primary colors CMYK with different tonal values. The reference numerals 1 refer to control fields of the primary color cyan (C), the reference number 2 on control fields of the primary color magenta (M), the reference symbols 3 on control fields of the Primary color yellow (Y) and reference number 4 on control subfields of the primary color achromatic Black (K). The letters a to f stand for different tonal values, with a for one Tone value of 100%, b for 80%, c for 60%, d for 40%, e for 20% and f for 5%. The reference number 2f therefore refers to a control field with the number 2 and letter e the primary color magenta (M) with an area coverage of 20%. The described Control fields are adjacent and arranged in an abutting manner.

The control subfields 4 of the primary color black correspond in this exemplary embodiment half of a multi-area control field 6, the size of the control fields 1, 2, 3 corresponds to the primary colors (CMY). The second control subfield is the colorful gray balance fields 5 taken. The control subfields are arranged so that always a gray balance field 5 an achromatic black grid field 4 with the same color impression opposite. For the sake of clarity, only the reference symbol in FIG. 1 is shown in FIG the control fields 6f formed in the sub-control fields 4f and 5f are exemplified.

This arrangement allows visual control of the gray balance fields in a direct comparison to the achromatic black grids, which represent the reference values. If the Printing process correct and the color reproduction is undisturbed, the two opposite should Control fields leave the same color impression. They give way Gray balance fields, however, from the achromatic black grid fields, so use Densitometer the color density of the primary colors in the full tone control fields 1a, 2a, 3a be measured to determine any discrepancies in the color densities.

Of course, any other gradation of the tonal values can be made become. Furthermore, the gradation of the tonal values with additional control fields or through Omission of control fields can be varied. In addition, the size and type vary the subdivision of the two-part control fields. However, it has proven to be beneficial proved that the multi-area control panels match the size of the control panels of the Correspond to primary colors (CMY).

3 shows the multi-area control fields 6 with the control subfields 4 and 5 according to FIG the description of FIG. 1.

FIG. 2 shows a color gradient control field 10 with a strip-shaped grid field 11 strip-shaped grid 11 reproduces the linear course which is continuous according to setpoints the tonal values from 0 to 100%. For reasons of space, FIG. 2 shows only a section of such a gradient control field 10.

To the side of the strip-shaped grid 11 is a value scale 12 with the associated ones Target values of the tonal values are arranged in percent. The gradation or resolution of the value scale can be any, in the present embodiment it has proven to be advantageous List tonal values in increments of 3% each.

The arrangement allows the color jump in the stripe form, visually or with a measuring device Determine grid 11 and the color jump on the basis of the associated associated Assign tone values to the corresponding tone value or tone value range.

The control strip or control block can also contain other control fields, such as control fields for the secondary colors red, green, blue from the overprint of the primary colors (CMY), Black (K), achromatic grids with a tone value of 50% with different grids, like dot and line grids, a Siemens star to check the resolution and / or contain a register field for checking the register shift.

Claims (12)

Control strips or control block, comprising an arrangement of control fields for checking and / or controlling the multicolor printing of a gravure printing process,
characterized in that
the control strip or control block contains multi-area control fields (6), each with a first (5) and a second control subfield (4), and a) the first control subfields (5) are colored gray balance fields from the overprinting of the primary colors cyan (C), magenta (M) and yellow (Y) in graded tonal values from 0-100% and b) the second control subfields (4) are achromatic grids of black (K) in graded tonal values from 0-100%, and the tonal values of the first (5) and second control subfield (4) of a multi-range control field (6) are selected such that the multi-range control field appears as a uniform tone area and the two control subfields of a multi-range control field are immediately adjacent to one another. Control strips or control block, containing an arrangement of control fields for checking and / or controlling multicolor printing for a gravure printing process,
characterized in that
the control strip or control block contains a color gradient control field (10) in the form of a strip-shaped grid (11) of the primary color black (K), the color gradient control field along its longitudinal extent having a gradient of the tonal values of 0-100% continuously increasing or decreasing according to target values reproduces and the associated target values of the tonal values (12) are listed in graded division on the lateral longitudinal edge of the strip-shaped grid. Control strips or control block containing an arrangement of control fields for checking and / or controlling the multicolor printing of a gravure printing process, characterized in that the control strip or control block contains multi-range control fields (6), each with a first (5) and a second control subfield (4), and a) the first control subfields (5) are colored gray balance fields from the overprinting of the primary colors cyan (C), magenta (M) and yellow (Y) in graded tonal values from 0-100% and b) the second control subfields (4) are achromatic grids of black (K) in graded tonal values from 0-100%, and the tonal values of the first (5) and second control subfield (4) of a multi-range control field (6) are selected such that the multi-range control field appears as a uniform tone area and the two control subfields of a multi-range control field are immediately adjacent to one another, and the control strip or control block contains a color gradient control field (10) in the form of a strip-shaped grid (11) of the primary color black (K), the color gradient control field (10) over its longitudinal extent having a gradient of the tonal values of 0 continuously increasing or decreasing according to target values -100% and the associated nominal values of the tonal values (12) are listed in graded division on the lateral longitudinal edge of the strip-shaped grid. Control strip or control block according to one of Claims 1 and 3, characterized in that the multi-range control fields are arranged adjacent to one another in the order of increasing or decreasing tonal values, preferably directly and abutting one another, the gray balance fields lying on a common axis and the achromatic, black grids are arranged lying on a common axis. Control strip or control block according to one of claims 1 and 3, characterized in that the individual color densities of the primary colors CMY from the gray balance fields are adapted to the printed substrate. Control strip or control block according to one of Claims 1 to 5, characterized in that the control fields contain single-color grid fields of the primary colors CMY in graded tonal values from 0-100%. Control strip or control block according to Claim 6, characterized in that the control fields of the individual primary colors CMY are arranged adjacent to one another in the order of increasing or decreasing tonal values and preferably directly and abutting one another. Control strip or control block according to one of Claims 1 to 6, characterized in that the first and second control subfields and / or the single-color grid fields of each primary color each contain a full-tone field (100%). Control strip or control block according to one of Claims 1 to 8, characterized in that the control strip or control block contains full-tone control fields for the secondary colors red, green and blue from the overprinting of the primary colors (CMY). Control strip or control block according to one of claims 1 to 9, characterized in that the control strip or control block contains control fields for blacks (K), achromatic grid fields with a tone value of 50% with different grid patterns, such as dot and line grids. Control strip or control block according to one of Claims 1 to 10, characterized in that the control strip or control block contains a control field in the form of a Siemens star for checking the resolution. Control strip or control block according to one of claims 1 to 11, characterized in that the control strip or control block contains a control field in the execution of a register field for checking the register shift.

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